Spawning Under the Map

Every time I join the game, I spawn and fall through the map into the water and die. I have noticed that all of the terrain in the game is missing for me, except for the roads. If I spawn on the road, I can walk around and what not, but all of the ground is still missing.
Anyway to fix this? Delete all the files and re install? If so where are the files located?
Any help would be great.

Try clearing your cache.